It is known to provide electrical power storage devices, such as batteries or cells, for use in vehicles such as automobiles. For example, lead-acid batteries have been used in starting, lighting, ignition, and other applications.
It is known to provide a battery cell that is made from an anode and a cathode (electrodes) separated by a permeable dielectric separator. In short, an electrode may be manufactured by stamping or punching a continuous sheet of lead or lead alloy material. The stamped material is processed to add active material, typically in the form of electrochemical paste. The electrochemical paste is typically a material (e.g. a viscous liquid) that sets or dries on the stamped material and contracts as it cures or hardens into a solid. After the paste is provided, the stamped material is cut into individual electrode plates, which may be used in stacked batteries.
The formed or stamped grid can have imperfections on the surface of the frame elements, such as burrs and the like. In some cases, burrs may form or be formed on or near one or more of the edges, corners or ends of the battery grid. Burrs and imperfections can contribute to separator failure and short circuits, particularly at the corners where pressure on the separator is relatively greater. These imperfections on the surface of the frame elements can also catch or snag on separator material used to separate positive and negative plates or electrodes.
As a lead-acid battery is charged positive electrode active material is converted from lead sulfate/lead oxide to lead dioxide. This chemical conversion to a larger molecule size causes the active material to expand, placing stress on the electrode grid. The stress can cause the grid to cup, which cupping effect is most prominent at the edges and corners of the grid. When the plates are stacked, the effect of this cupping can be cumulative to create points of increased pressure. For example, the effect of a series of cupped plates that are cupped in the same direction is cumulative, becoming more pronounced with each successive plate. Furthermore, adjacent plates with cupped sides facing each other create pinch points, particularly at the corners where the cupping effect may more pronounced.
These effects can put excessive pressure on the separators that are provided between adjacent plates. In addition, the corners of a positive grid have been known to pierce or cut the separator material as the grid cups against the negative plate, leading to shorts and battery failure.
Moreover, battery grids have been known to grow over time as the grid goes through its lifecycle, often due to corrosion. The grid growth may result in shorting of a battery cell, and battery failure.